Ethereum Message Signing on PHP

readme.md

Install

composer require digitaldonkey/ethereum-php

Usage

PRIVATE_KEY=0x.. CHAIN_ID=1 php -S 0.0.0.0:8080 signer.php

composer.json

{
  "minimum-stability":"dev",
  "autoload": {
    "psr-4": {
      "Ethereum\\": "src/"
    }
  },
  "repositories": [
    {
      "type": "git",
      "url": "https://github.com/digitaldonkey/ethereum-php.git"
    }
  ],
  "require": {
    "digitaldonkey/ethereum-php": "dev-master"
  }
}

signer.php

<?php
require __DIR__ . '/vendor/autoload.php';
use Ethereum\EthereumStatic;
use Elliptic\EC;

$secret_key = getenv("PRIVATE_KEY");
$chain_id = getenv("CHAIN_ID");
$uri = $_SERVER["REQUEST_URI"];
header("Content-Type: application/json");
preg_match("|^/api/v1/ethsign/(0[xX][0-9a-fA-F]{40})$|", $uri, $matches);
if(!$matches) {
    header("HTTP/1.1 404 Not Found");
    echo json_encode(array("status"=>"not_implemented", "status_code"=>404, "x"=>$uri));
    exit();
}
$address = strtoupper($matches[1]);
$data = sprintf("%s:%d", $address, $chain_id);
$msg = sprintf("\x19Ethereum Signed Message:\n%s%s", strlen($data), $data);
$hash = EthereumStatic::sha3($msg);
$signer = (new EC('secp256k1'))->keyFromPrivate($secret_key);

$signature = $signer->sign($hash, "hex", array("canonical"=>true));
echo json_encode(
    array(
        "signature"=>sprintf(               
            "0x%s%s%02x",                   
            $signature->r->toString("hex"), 
            $signature->s->toString("hex"), 
            $signature->recoveryParam + 27  
        ),
        "address"=>$address,
        "hash"=>$hash,
    )
);
?>